With the rear aperature nearly in identical places an abrupt shift in cheek weld isn't about the rear sight. They are all within fractions of an inch in the same place.
I bought a used carry handle rear sight and cut off the front portion, as have a lot of others on boards. It's milspec - it's the right height - it clamps on and fits - it's 2MOA accurate per contract specs - it's cheap - it takes abuse and has few parts to fail, collapse, or break - it's instantly ready like it should be when you need it because you don't have to take seconds getting it up into working position.
If you choose to keep the rest of it attached, it protects you from the cheese grater rail when carrying.
Millions of soldiers, sailors, airmen, and Marines were taught, qualified, and actually used the sights in combat for 30 years and they work. We may have moved to red dots in the last ten years, but it doesn't make the glass in them unbreakable, nor will they put up with being run over by a truck, like that's a measure of anything. Neither will iron sights, but they do put up with falling out of the back of a 5 ton truck, getting banged around in bayonet drills or CQB, and with the optional aftermarket front posts, can be made more visible in bad light.
Iron sights aren't that bad - I was never issued a red dot, I only have owned one since the first generation Aimpoint on my hunting rifles. Red dots are nice to have, but they are more expensive than iron sights and they must be protected just as any other glass lensed scope. The light equipment repair companies stationed overseas report they have to replace the issue red dots constantly due to breakage of the lenses, and have shipping containers of broken ones returning to CONUS after deployment.
Red dots aren't there yet, the carry handle sight has been there, done that for nearly two hundred years in principle, and 45 years in application on the M16/M4. I wouldn't discount them as obsolete yet.